Metal photographic plate comprising a photoconductor and process

ABSTRACT

A METALLIC BASE PHOTOGRAPHIC PLATE HAVING IMAGES ADHERENTLY AND PREFERABLY CONDUCTIVELY BONDED TO THE METALLIC SUPPORT IS PRODUCED BY EXPOSING A COPY MEDIUM COMPRISING A PARTICULATE PHOTOCONDUCTOR ON A SUPERFICIALLY ROUGHENED METALLIC SUPPORT WHEREIN THE PHOTOCONDUCTOR IS SUBSTANTIALLY PHOTOCONDUCTIVELY INSULATED FROM THE METALLIC SUPPORT, AND CONTACTING THIS COPY MEDIUM WITH CHEMICALLY REACTIVE IMAGE-FORMING MATERIALS, SUCH AS A PHYSICAL DEVELOPER. A PREFERRED PROCESS IS ONE UTILIZING A COPY MEDIUM CAPABLE OF BEING RAPIDLY PROCESSED AND HAVING A LAYER OF A PHOTOCONDUCTOR-BINDER EMULSION ON A ROUGHENED METALLIC SUPPORT AND A PHYSICAL DEVELOPER CAPABLE OF PRODUCING AN IMAGE ADHERENTLY AND CONDUCTIVELY BONDED TO THE METALLIC SUPPORT. THE PLATE PRODUCED BY THIS INVENTION IS USEFUL AS A PRINTING PLATE, NAME PLATE, PRINTED CIRCUIT AND THE LIKE.

United States Patent tion Ser. No. 744,631, July 15, 1968. This application July 13, 1970, Ser. No. 54,626 Claims priority, application Great Britain, July 14, 1969, 35,290/ 69 Int. Cl. G03f 7/02 U.S. Cl. 96-33 17 Claims ABSTRACT OF THE DISCLOSURE A metallic base photographic plate having images adherently and preferably conductively bonded to the metallic support is produced by exposing a copy medium comprising a particulate photoconductor on a superficially roughened metallic support wherein the photoconductor is substantially photoconductively insulated from the metallic support, and contacting this copy medium with chemically reactive image-forming materials, such as a physical developer. A preferred process is one utilizing a copy medium capable of being rapidly processed and having a layer of a photoconductor-binder emulsion on a roughened metallic support and a physical developer capable of producing an image adherently and conductively bonded to the metallic support. The plate produced by this invention is useful as a printing plate, name plate, printed circuit and the like.

This application is a continuation-in-part application of U.S. Ser. No. 744,631, filed July 15, 1968, now abandoned.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to metallic base photographic plates.

(2) Description of the prior art Metallic base photographic plates having an image adherently bonded thereto are particularly useful for nameplates or printing plates. However, prior art methods of producing such plates suffer a number of disadvantages. For example, U.S. Pats. 2,115,339; 2,126,017; and 2,766, 119 disclose processes wherein silver halide is impregnated in the surface of an anodized aluminum substrate by submerging the substrate successively in a solution of a halide and a solution of a soluble silver salt, thereby forming silver halide in situ. Special care must be taken to treat the anodized aluminum surface prior to forming the silver halide in order that the exposed aluminum in the pores is covered up. Otherwise deterioration of the silver halide occurs with time. Furthermore, because of the way the silver halide is formed in the surface of the metallic layer only about one third of the volume of the pores are filled. Therefore, it is difiicult to obtain images having uniform optical density by chemical or by physical development. Since the silver halide in the unexposed areas is insoluble, in order to fix the finally developed print it is necessary to dissolve out the insoluble compounds remaining unexposed. The plates resulting from this process have poor printing properties and because of the complexity of the process the manufacturing costs are high.

British Pat. No. 1,064,726 discloses the process wherein materials such as an aromatic diazosulphonate is deposited in the pores of an anodized aluminum support. Since the photosensitive material of this system is reactive with the aluminum it is likewise necessary to pretreat the anoice dized aluminum support with a material which absolutely prevents contact between the aluminum and the photosensitive material. An additional limitation of this system is that excessive fogging occurs unless a number of steps are taken. For example the concentration of mercuric ion may be adjusted in the nuclear introduction bath, by treatment of the oxide layer preceding the sensitization thereof with a bath containing mercuric ions, or by adding an organic hydroxy-acid to the nuclear-introduction bath. An additional disadvantage of this system is that mercury salts present serious toxicity problems. The complexities of this system also would result in high manufacturing costs. Therefore, to date, this system has not been important commercially.

R. F. Reed, Ofiset Lithographic Plate Making, 1967, teaches a number of different commercial processes for producing metal plates for printing. Such processes are generally rather complicated and time-consuming. Exemplary of such a process is the deep etch plate which is prepared by exposing a metallic plate containing a coating of gum arabic and ammonium bichromate, developing the plate with special solution to dissolve the unhardened coating from the image areas, applying a special acid solution to etch away metal from the image areas, copperizing the image areas by an electroless plating bath or by an electrolytical method, applying a special lacquer and ink to the etched image areas, soaking the gum in the non-image areas and scrubbing it off from these areas, and finally applying a plate etch to desensitize these areas. Therefore, although the deep etch plate process produces high quality long run printing plates capable of producing printing runs of 100,000 copies or more, the cost of such plates is extremely high since these plates must be prepared manually by means of skilled labor. Although this process has been around for more than half a century, attempts to produce these high quality long run metal imaged metallic printing plates by substantially simplified and more economical procedures have failed.

It is the desire of this invention to produce a metallic base plate having quality metallic images which are adherently and preferably conductively bonded to the metallic support and can be used for making a long run printing plate, a name plate, printed circuit, or the like by means of a process which is rapid, simple, and economical. Preferably this process will be done mechanically.

In our copending application, U.S. Ser. No. 446,707, filed Apr. 8, 1965, (now abandoned) a process is described wherein a copy medium comprising an adherent film of titanium dioxide deposited on an aluminum support is exposed and physically developed to produce a metal image on the surface of the support. The titanium dioxide is applied to the aluminum support as an adherent coating by first applying a compound which forms titanium dioxide when heated to elevated temperatures such as from about 400 C. to about 900 C. Such a copy medium solves many of the problems of the prior art since the photosensitive material does not deteriorate upon contact with the bare aluminum. Moreover, the copy medium may be stored in light or darkness without deterioration. Additionally the copy medium may be exposed imagewise and processed very simply and rapidly to produce an image having good density.

One of the serious problems which the system of U.S. Ser. No. 446,707 presents is that the relau'vely long time required to heat the copy medium at the relatively high temperatures make the copy medium uneconomical for many purposes. Additionally many substrates have coatings which cannot withstand the high temperatures of this process, and, therefore, such substrates which are otherwise desirable for surface properties, aesthetic reasons, and the like cannot be used.

3 SUMMARY OF THE INVENTION A metallic base photographic plate having images adherently and preferably conductively bonded to the metallic support is produced by exposing the copy medium of this invention and contacting this copy medium with chemically reactive image-forming materials, such as a physical developer. The copy medium useful in this invention comprises a particulate photoconductor, such as TiO on a superficially roughened metallic support wherein the photoconductor is substantially photoconductively insulated from the metallic support. A preferred process is one utilizing a copy medium wherein the photoconductor is carried in a binder on the metallic support. Preferably the photoconductor is photoconductively insulated from the metallic support by means of a solvent impermeable layer, preferably having a thickness of at least 14 A. units. The plate produced by this invention is useful as a printing plate, name plate, template, advertising plate, scale, printed circuit and the like. The imaged plate may be used as by contacting with a photographic fixer. Preferably, however, the photosensitive layer and optionally the binder and/or insulating layer may be removed, as for example, by washing, thereby exposing an image adherently bound to the metal support.

When the imaged plate of this invention is used as a printing plate it is generally desirable to increase the oleophilic-hydrophilic differentiation between the imaged areas and the non-image areas of the metal plate. This may be done, for example, to a silver image which is deposited on an aluminum support by contacting with materials such as mercaptans which will adhere to the silver image areas making them more oleophilic, alone, or in combination with phosphoric acid which adheres to the non-image areas thereby making the non-image areas more hydrophilic. Also a lithographic preparation containing a polymer such as gum arabic or carboxymethyl cellulose can be applied to improve the hydrophilic character of the non-image parts of the plate. Additionally, the printing life of the plate as well as the oleophilic character may be improved by coating the plate with lacquers which will adhere selectively to the image areas and not to the non-image areas. Other useful compounds for increasing the printing properties of this metal plate are disclosed in French Patent of Addition No. 77,556, herein incorporated by reference. A silver germ image or an amplified silver image may be made more oleophilic by amplifying in a metal ion both which will produce an image more oleophilic than a silver image, e.g. a copper image.

When the imaged plates are used as nameplates a colored developer may be used or a colored lacquer may be used which selectively adheres to the image areas. These plates may then be coated with an ordinary transparent coating, if desired.

PREFERRED EMBODIMENT(S) The copy medium preferably used in this invention comprises a metallic base photographic plate capable of being stored in light or darkness without deterioration of its photosensitive components and capable further of being physically developed comprising a photoconductor which becomes reversibly activated and substantially chemically unchanged upon exposure to activating radiation and is capable of causing chemical reaction in the exposed areas, this photoconductor being deposited upon a superficially roughened metallic support and the photoconductor being substantially photoconductively insulated from the metallic support. The photoconductor of this invention is of a particulate nature and is preferably incorporated in a photoconductively insulating binder and deposited as a very thin layer upon the superficially roughened metallic support in such a way that the photoconductor is impregnated within the roughened portion of the support. This is readily accomplished, for example, by depositing a photoconductor, such as TiO in a solvent-binder solution of relatively low viscosity and then coating this composition onto the roughened metallic support. The coating composition may be allowed to dry. Such a metallic support which has a photoconductor-binder coating will preferably have a very thin coating which is solvent permeable and will thereby allow rapid processing in the preferred developer systems.

The roughened metallic support of this invention is a metallic support which has been physically, chemically, or otherwise roughened in order that the metallic image forming materials are adherently bonded to the support. Physically roughened supports which are suitable for this invention are onces having grained, porous, or matted surfaces. Chemically roughened supports are ones which have been treated by suitable acids or bases, adhesive primers, adhesives, and the like to cause chemical bonding to take place between the image forming materials and the surface of the support. Additionally, additives such as cadmium and/or zinc salts may be added to the image forming materials in a manner such as taught in French Patent of Edition No. 77,556 in order to improve the adhesion of the metal image to the metallic support. Also certain alloys, such as the manganese aluminum alloy (for example, containing 1 to 2% manganese), provide good adhesion for the deposited metal image. The term roughened supports, therefore, is intended to include a physically smooth support which by chemical or other means provides an adhesive bond with the metal image deposited thereon.

The thickness of the photosensitive layer or the imageforming layer and the insulating layer will depend upon the nature of the photosensitive material, the nature of the binder, the amount of activating radiation utilized, and other like factors. However, in order to obtain an imaging medium capable of rapid processing it is preferred that these layers be relatively thin, preferably less than about two microns in thickness. Most preferably, the substrate is coated with a binder-photoconductor layer of less than about one micron in thickness in order to obtain the rapid processing which is most desired.

In general the amount of binder to amount of photoconductor or other photosensitive material may vary over wide ranges. Preferably, from about 1 part by weight to about 6 parts by weight of photosensitive material per part by weight of binder will be used. However, if desired the binder may be omitted.

In the embodiment wherein a photoconductor is immersed in the roughened surface of a metallic support the photoconductor should be insulated from the metal of the support. This insulation may be provided by the binder in which the photoconductor is dispersed, a separate insulating layer such as a silicate layer, metal oxide of the metal of the support, or the photoconductor itself may act as an insulating layer if it is sufficiently thick.

The insulating layer of this invention is one which will photoconductively insulate the photoconductor or other photosensitive material. A Photoconductive insulator as herein defined is one which will act to substantially prevent the passage of electrons from the activated photoconductor caused by exposure to activating radiation to the conducting metallic support.

The insulating layer of this invention is preferably a solvent impermeable layer of at least 14 A. in thickness and more preferably at least about 20 A. in thickness. Below about 10-14 A. in thickness the photographic speed is very low and the background fog is extremely high. Also when the insulating layer is less than about 14 A. in thickness a reversible latent image produced by exposure to activating radiation decays so rapidly that development must take place within a few seconds in order to obtain any image at all. When the insulating layer is at least about 20 A. in thickness, the development latitude is greatly increased, i.e. the time of development or concentration of the developer, eg the metal ions, may be increased above the optimum without getting significant background fog. An especially preferred. ins

ing layer is one produced by oxidizing the surface of the metallic substrate. This barrier oxide layer can be produced by anodizing techniques, mild electrical treatment, heating in an oxidizing atmosphere, or by treating with acids such as nitric, citric, or malytic acid. A preferred system of producing such an oxidized metal surface is by first degreasing the metal such as aluminum with pumice or soap, then graining the metal substrate, as for example, by brush graining by means of nylon brushes, then washing the metal substrate, then applying an oxide layer by a method such as mentioned above, then applying the photosensitive coating, and finally drying the coated substrate. Preferably, the operation is done in line from coil metal. When coil metal is utilized a cutter is provided at some point in the operation, preferably at the end to cut the coated substrate into desired sizes.

A most preferred substrate is an aluminum support having a barrier oxide layer of at least 14 A. in thickness and most preferably at least about 20 A. in thickness.

The photoconductor or photocatalyst preferred in this invention are metal containing photoconductors. A preferred group of such photosensitive materials are the inorganic materials such as compounds of a metal and a non-metallic element of Group VI-A of the Periodic Table such as oxides, such as zinc oxide, titanium dioxide (TiO zirconium dioxide, germanium dioxide, indium trioxide; metal sulfides such as cadmium sulfide, zinc sulfide and tin disulfide; metal selenides such as cadmium selenide. Metal oxides are especially preferred photoconductors of this group. TiO is a preferred metal oxide because of its unexpectedly good results. Ti0 having an average particle size less than about 250 millimicrons and which has been treated in an oxidizing atmosphere at a temperature exceeding about 200 C. is especially preferred, and more especially that Ti0 produced by high temperature pyrolysis of titanium halide.

Also useful in this invention as photoconductors are certain fluorescent materials. Such materials include, for example, compounds such as silver activated zinc sulfide, and zinc activated zinc oxide.

While the exact mechanism by which the photoconductors of this invention work is not known, it is believed that exposure of photoconductors or photocatalysts of this invention to activating means causes an electron or electrons to be transferred from the valence band of the photoconductor or photocatalyst to the conductance band of the same or at least to some similar excited state whereby the electron is loosely held, thereby changing the photoconductor from an inactive form to an active form. If the active form of the photoconductor or photocatalyst is in the presence of an electron accepting compound a transfer of electrons will take place between the photoconductor and the electron accepting compound, thereby reducing the electron accepting compound. Therefore a simple test which may be used to determine whether or not materials have a photoconductor or photocatalytic effect is to mix the material in question with an aqueous solution of silver nitrate. Little, if any, reaction should take place in the absence of light. The mixture is then subjected to light. At the same time a control sample of an aqueous solution of silver nitrate alone is subjected to light, such as ultraviolet light. If the mixture darkens faster than the silver nitrate alone, that material is a photoconductor or photocatalyst.

It is evident that the gap between the valence and the conducting band of a compound determines the energy needed to make electron transitions. The more energy needed, the higher the frequency to which the photoconductor will respond. It is known to the art that it is possible to reduce the band-gap for these compounds by adding a foreign compound as an activator which either by virtue of its atomic dimensions or by possessing a particular electronic forbidden zone structure or through the presence of traps as donor levels in the intermediate zone between the valence and the conduction band stresses the electronic configuration of the photoconductive compound, thereby reducing its band-gap and thus increasing its ability to release electrons to its conduction band. Phosphors almost necessarily imply the presence of such activating substances. The effect of such impurities may be such as to confer photoconductivity upon a compound which intrinsically is non-photoconductive. On the other hand, excessive impurity content can interfere with a compound acting as a photoconductor, as above described.

The photoconductors of this invention may be sensitized to visible and other wavelengths of light by foreign ion doping, addition of fluorescent materials, and/ or by means of sensitizing dyes. Bleachable dyes useful for sensitizing the photoconductors of this invention include, for example, the cyanine dyes, the dicarbocyanine dyes, the carbocyanine dyes, and the hemicyanine dyes. Additional dyes which are useful for sensitizing the photosensitive medium of this invention are the cyanine dyes described on pages 371-429 in The Theory of Photographic Process by C. E. Kenneth Mees, published by McMillan Company in 1952. Other useful dyes include those known to the art as triphenylmethane dyes such as crystal violet and basic Fuchsin, diphenylmethane dyes such as Auroamine O, and Xanthene dyes such as Rhodamine B.

Latent images formed by exposure of a copy medium comprising a photoconductor or germ images formed by contacting the latent image prior to, during, or subsequent to exposure with an image-forming material such as a solution of metal ions may be of the internal type which are closely associated with the metallic support or may be of the external type which are separated from the metallic support by an insulating layer. For example, the insulating layer may be a solvent-permeable binder layer, an unexposed photoconductor layer, or the like.

Irradiation sources which are useful in this invention for producing the initial latent image include any activating electromagnetic radiation. Thus actinic light, X- rays, or gamma rays are effective in exciting the photoconductor. Beams of electrons and other like particles may also be used in the ordinary forms of electromagnetic radiation for forming an image according to this invention. These various activating means are designated by the term activating radiation.

The metallic support of the imaging medium of this invention comprises any suitable metallic or substantially metallic backing of sufiicient strength and durability to satisfactorily serve as a reproduction carrier. The sup port may be in any form such as, for example, sheets, ribbons, rolls, etc. This sheet may be made of any suitable metal or their alloys, as for example, the hydrophilic metals such as chromium, nickel, lead, stainless steel, magnesium, or aluminum; or the oleophilic metals such as copper or zinc. Aluminum is preferred because of its desirable physical and chemical properties, as well as its economy. A porous anodized surface is especially preferred for the aluminum support. The anodized surface may be sealed by heating. However, the unsealed surface is preferred because of the improved adhesion that can be obtained between the metal image and the aluminum support.

The support and imaging metal may be chosen so as to give a good oleophilic-hydrophilic differentiation for use in a lithographic process. Also by special treatments or the right substrate or imaging metal, this process can be used to produce a plate useful in the so called driographic manner described in US. 3,511,178.

It may be desirable to use a binder agent to bind the photoconductor to the base sheet to aid in improved physical development, or to use a separate insulating layer. In general, these binders are translucent or transparent so as not to interfere with transmission of light therethrough. They are desirably also solvent permeable in order to allow rapid physical development to take place. Preferred binder materials are organic materials such as natural or synthetic polymers. Examples of suitable synthetic polymers are butadiene-styrene copolymer, poly (alkyl acrylates) such as poly (methyl methacrylate) polyamides, polyvinyl acetate, polyvinyl alcohol and polyvinylpyrrolidone. Natural polymers such as gelatin are also useful. Most preferred are those binders which are solvent soluble enough to be readily washed off after development of the image has taken place.

The photoconductor should be conditioned for ex posure by storage in the dark from one to twenty-four hours prior to use, heating or other conditioning means known to the art. After conditioning, the photoconductor is not exposed to activating radiation prior to its exposure to activating radiation for recording an image pattern.

The period of exposure to form the latent image will depend upon the intensity of the light source, particular photoconductor, the type and amount of catalyst, if any, and like factors known to the art. In general, however, the exposure may vary from about 0.001 second to several minutes.

Physical developers according to this invention are intended to include those image-forming systems such as described in U.S. Pats. 3,152,903 and 3,390,988, and in British Pats. 1,043,250 and 1,064,725, each incorporated herein by reference. These image-forming materials include preferably an oxidizing agent and a reducing agent. Such image-forming materials are also often referred to in the art as electroless plating baths. Electrolytic development such as taught in U.S. Pat. 3,152,969 can also be used. The oxidizing agent is generally the image-forming component of the image-forming material. However, this is not necessarily true. Either organic or inorganic oxidizing agents may be employed as the oxidizing component of the image-forming material. The oxidizing and reducing agent may be combined in a single processing bath, may be in a separate bath, or a separate nucleation bath may precede the physical development. Also one or both of the oxidizing and reducing-agent components may be incorporated in the imaging medium prior to exposure. Preferred oxidizing agents comprise the reducible metal 'ions having at least the oxidizing power of cupric ion.

These oxidizing agents also include such metal ions as Ag Hg, Pb, Au+ |Au+ H, H, M, Sn, Pb+ Cu, and Co.

The reducing agent component of the image-forming materials of this invention are inorganic compounds such as the oxalates, formates, and ethylenediaminetetraacetate complexes of metals having variable valence; and organic compounds such as dihydroxybenzenes, aminophenols, and aminoanilines. Also, polyvinylpyrrolidone, hydrazine, and ascorbic acid may be used as reducing agents in this invention. Suitable specific reducing compounds include hydroquinone or derivatives thereof, and p-aminophenol, p-methylaminophenol sulfate, p-hydroxyphenyl glycine, oand p-phenylenediamine, l-phenyl-3-pyrazolidone, alkali and alkaline earth metal oxalates and formates.

Liquid physical developer systems are preferred for use as image-forming materials because of the excellent results obtained therewith. Any suitable solvent 'may be utilized. However, aqueous processing baths are preferred. While the pH of the developer is not critical, it has been found the best results are obtained with an acid developer, and especially one having a pH of between about 2 and 5, and especially with organic acids such as citric, gluconic, maleic, and oxalic which are metal complexing agents. A pH of about 2 to 3 is especially preferred. It is believed that the acid functions by dissolvmg the oxide layer on a metal such as aluminum, therefore improving the adhesion and conductivity of the image to the metallic support.

Additionally, the image-forming materials or physical developers may contain organic acids or alkali metal salts thereof, which can react with metal ions to form complex metal anions. Further, the developers may contain other complexing agents and the like to improve image formation and other properties found to be desirable in this art.

Additional developer systems useful in this invention are those disclosed in the following U.S. 3,674,489, entitled Photographic 'Image Amplification With Copper Ions, Ser. No. 743,982, entitled Photographic Tin Amplification Process and Product; now abandoned; U.S. 3,645,736, entitled Physical Development Systems, Processes, and Related Materials; each of which is incorporated herein by reference.

The physical developers of this invention should be applied for a length of time sufficient to obtain an image adherently and preferably conductively bound to the metallic support. Preferably the physical development is allowed to proceed until a coherent metal image rather than a particulate metal image is produced. This time period will vary according to the thickness of the photoconductor layer, thickness of the insulating layer or other separation layers, whether the latent image or metal germ image being amplified is of the internal or external type, the length of exposure, nature of the hinder or insulator material, ratio of photosensitive material to binder, and like factors known to the art.

A useful plating bath for amplifying a metallic image which is conductively bonded to a metal support is the one comprising a metal ion and a pickling agent for the metal of the metallic support, e.g. a solution of copper ethylenediaminetetraacetic acid (CwEDTA) and sodium EDTA, which is disclosed in our U.S. patent application field on even date entitled Metal Coating Process, D-890, incorporated herein by reference.

While this application generally describes a negative working (i.e. negative to positive or visa versa) photographic process, it should be understood that the process applies equally well to positive working processes such as described in commonly owned U.S. 3,718,465, U.S. 3,711,283, or U.S. 3,414,410.

The metal image of this invention is a coherent metal as opposed to the particular metal of most photographic images. Rnthermore, these images are adherently bonded to the support. The type of image metal plus the bonding to the support gives the plate the capability of being used on a conventional offset lithographic printing press under ordinary operating conditions to produce at least 5,000 inked paper prints, and more preferably at least 100,000 without showing any significant loss in print quality.

A process according to this invention for making ink printing plates and using these plates for printing which comprises: contacting an imaging medium comprising a physically developable image with a metal image-forming material for a period of time sufficient to produce a coherent, conductive metal image adherently bonded to the medium; contacting the surface of the imaged medium with a printing ink which selectively adheres to the image or non-image areas; and, contacting the ink medium with a receptor sheet for said ink. Preferably a lithographic printing process is used treating the surface of the imaged medium with an aqueous fountain solution, and may be used on a lithographic press without the fountain solution to print by driography. In driographic printing the nonimage areas of the plate are made to reject oleo ink, e.g. by coating with a polysiloxane elastomeric polymer. With a printing ink having an oleophilic binding agent, whereby said ink adheres to the areas of the surface corresponding to the physically developable image, and using said ink imaging medium to print by lithography, alternatively a low tack ink.

This invention above described is exemplified as follows:

EXAMPLE 1 A brush grained aluminum sheet material of about .009 inch in thickness is coated with finely divided TiO dispersed in a slightly hydrolyzed polyvinyl alcohol binder. An aqueous Tio -polyvinyl alcohol coating formulation is applied with a #4 Mayer rod to a thickness of about 4.0x 10" inches.

After drying, the printing plate thus produced is exposed to an image pattern from a light source (quartz iodide lamp) for 5 seconds duration, thereby giving an exposure of 80,000 meter candle seconds, producing a latent image on the plate medium.

The thus exposed plate is then immersed in an aqueous solution of 3 N silver nitrate for seconds, allowed to drain, then immersed in an aqueous developing solution having a pH of about 2.5 comprising the following:

Polyethylene glycol tertdodecyl thioether surfactant) Citric acid Water to a liter.

and then immersed in a sodium thiosulfate fixing bath. The coating is washed from the surface of the plate, a visible image of good density is produced on the thus treated medium. The silver image is deposited in the surface of the aluminum sheet. Attempts to erase the visible image by means of vigorous abrasion from a pencil eraser or by application of Scotch Brand Transparent Tape on the image areas and then ripping the tape oif vigorously without removing the images from the plate indicates that the image is truly imbedded in the surface of the grained aluminum sheet. An ohmmeter is used to test the conductance of the image and non-image areas. Much greater conductance is shown in the image areas as compared with the non-image areas, thus showing that the image is conductively bound to the aluminum support.

The plate is then treated with the following electroless copperizing solution:

Just prior to use, Solutions I and H are mixed. The plate is immersed for 3-5 minutes. The results of this treatment is the copper plating of the imbedded silver image areas only. The thus copper imaged plate is then treated with a dilute solution of phosphoric acid (H PO and inked with rub-up ink. The plate is now used for printing on an offset press to run off one hundred thousand (100,000) copies. Good continuous tone and half tone prints are produced. The print has a resolution of 200 lines per mm.

As an alternate procedure to contacting with the electroless copperizing solution, the silver imaged aluminum plate is contacted with a copper electroplating bath which plates out copper selectively in the silver image areas of the plate. This thus imaged plate is then used on a lithographic press for producing multiple copies.

EXAMPLE 2.

A brush grained aluminum foil or sheet is coated, exposed and developed as explained in Example 1 to produce an aluminum plate with a silver image adherently bound to the grained aluminum foil. However, the plate is not treated with a copperizing solution. The deposited silver image is instead treated with the following dispersron:

Gms. 2-mercaptobenzothiazole 1.0 85% H PO 1.0 Water 80.0

The dispersion is wiped on the plate with a cotton swab. The plate is now used on an oifset press. The silver image itself will now accept the greasy printing ink and the nonexposed background areas accept water.

EXAMPLE 3 PART I 3 N AgNO Cc-.. 15

PART II Gms. Metol (Eastman) 30 Citric acid B 0 to one liter.

I and II are mixed just prior to use. After the image has developed to a high density the coating is washed with water. The thus produced silver image is adherently bound to the aluminum foil. This silver image has improved printing properties as compared with the image produced in Example 1 wherein the exposed plate was contacted with the silver nitrate solution and the Metol solution in separate steps. These improved printing properties were noted by the greatly improved uniformity of the images in the final copy from the printing press. The above procedure may be performed by hand or by a machine having an exposure station, a mixing means, an applicator or dip station, and a wash station in combination with a means for transporting the plate to the various stations.

The thus developed sheet is next treated with the following copperizing solution:

M CuSo .5 Sodium ethylenediame-tetraacetate (Na EDTA) 1 A dense copper image adherently bound to the aluminum support is produced by contact with the copperizing solution at a temperature of 55 C. for 30 seconds. The ink receptivity of the resulting copper image is then improved by contacting with phosphoric acid, Bi- Kern copper activator or other solutions of this type. After treatment with activator the plate is treated with a rub-up ink and used on an oifset press for producing multiple copies of high quality.

EXAMPLE 4 The procedure of Example 1 is repeated utilizing the same materials except that Ti0 is used without a binder. However, after applying the aqueous TiO is used without a binder. However, after applying the aqueous Ti0 slurry formulation a rubber squeegee is used to remove any coating except that which is in the grain of the roughened 1 1 surface. An adherently bound silver image of good quality is produced.

EXAMPLE 5 An unsealed, porous, anodized aluminum sheet which is made of an aluminum alloy having 1.5% of manganese is coated as described in Example 1 and processed with the following viscous solutions:

VISCOUS SENSITIZER AgNO Gms 255 (Hercules Powder) Klycel H.A. (thickening agent) 15 To a liter with Water.

VISCOUS DEVELOPER Gms.

Metol 33.6 Diethylaminoethanethiol HCl 1.0 Citric acid 5.0

Pectin 30.0

EXAMPLE 6 A roughened aluminum sheet is coated and processed as described in Example 2 to produce adherently bound silver images on the roughened support. However, the image areas are subjected to the additional treatment:

(1) Coat with Durolith-250 lacquer or any other similar lacquer which adheres to oleophilic surfaces in preference to hydrophilic surfaces.

(2) Spray or coat with a clear ordinary coating lacquer and dry.

The imaged aluminum sheet thus processed is suitable for label or any similar metal decorating application. By omitting the step of coating with a clear, ordinary coating lalicquer, the thus lacquered support is useful as a printing p ate.

A brush grained or matted steel support is used in this example in place of the aluminum support to obtain similar results.

EXAMPLE 7 A brush grained aluminum support coated with a solvent permeable nitrocellulose coating is coated with an aqueous slurry of titanium dioxide and allowed to dry. The thus produced plate is then exposed and processed in a physical developer comprising silver nitrate and of Metol which is acidified with an aluminum complexing acid. A silver image which is adherently and conductively bound to theh aluminum support is produced. The silver image is covered with the nitrocellulose coating when the TiO slurry is washed off. The imaged support is useful as a nameplate.

Zinc oxide is substituted for the titanium dioxide in this example to obtain similar results.

EXAMPLE 8 A brushgrained aluminum sheet of about .006 inch in thickness is coated with a finely divided TiO dispersed in a gelatin binder. This coating has a dry thickness of about 1.2x 10- cm.

After drying the printing plate thus produced is exposed to an image pattern from an ultraviolet light source (a quartz iodide lamp) for 0.5 second duration, thereby giving an exposure of 8,000 meter candle seconds and producing a latent image on the copy medium.

The thus exposed copy medium is then immersed for 30 seconds in an aqueous solution of 1.0 normal silver nitrate, then immersed 30 seconds in an aqueous develop ing solution comprising Metol and sodium sulphite, and then immersed in a sodium thiosulfate fixing bath. A visible image of good density is produced on the thus treated copy medium.

The Ti0 -gelatin emulsion is then washed from the surface of the aluminum copy medium. to disclose a silver image imbedded in the surface of the aluminum foil. Attempts to erase the visible image by means of vigorous abrasion from a pencil eraser or a similar tool indicates that the image is truly imbedded in the surface of the grained aluminum surface.

The thus produced print is suitable for use as a name plate or tag or for use as a lithographic master.

As an alternative procedure a silicate coated, brush grained aluminum support is used in this example. A silver image is produced having good adhesion to the support.

A support which is chemically grained by treating with a sodium hydroxide and then Washing with phosphoric acid is used in the above example. This results in a plate having a final metal image having excellent adhesion to the aluminum support.

EXAMPLE 9 A brush grained aluminum plate with a thin photosensitive coating of TiO in a water soluble poly (vinyl alcohol) binder having incorporated therein a cyanine dye sensitizer is exposed for 20 seconds through a negative with a photofiood lamp having a spectral output primarily in the visible, held 10 seconds, then immersed in 0.01 M silver nitrate for 10 seconds. The specimen is then immediately dipped into a solution which is 0.2 M in Cu EDTA and contains 2 g. Metol and 7.5 g. Na SO for thirty seconds and immediately developed in Ti EDTA for 15 seconds. The photosensitive coating is then removed by washing in cold water, which also largely removes the image. However, some copper is deposited in an imagewise manner on the brush-grained surface. This image is not in contact with the aluminum as is evidenced by the fact that the copper image is not amplified when the copy medium is placed in a Cu EDTANa EDTA plating bath.

The brush grained aluminum oxide coating is penetrated in an imagewise fashion by cycling the above specimen between the Cu EDTA bath and the Ti EDTA bath, forming a copper image cemented to the aluminum substrate. This copper image is in electrical contact with the aluminum support as is shown by the amplification of this image which occurs when the copy medium is placed in a Cu ED-TANa EDTA plating bath. This plate is then used with an oil base ink on an offset press for making multiple copies.

One particularly notable advantage of the process of this invention is that a permanent image is obtained by merely removing the photosensitive layer. This is done chemically, e.g., by washing with a solvent, or mechanically, by peeling, scraping, and the like.

EXAMPLE 10 An unsealed anodized aluminum support is coated with a solution of silver nitrate in a water permeable binder and dried. This thus coated substrate is then coated with a slurry of TiO in a water permeable binder and dried. The thus prepared copy medium is then exposed imagewise to light, contacted briefly (1-10 seconds) with a solution of Metol-phenidone acidified with citric acid 1-5 seconds, washed to remove the binder layers, and finally treated with the copperizing solution of Example 1 leaving a copperized silver image adherently and conductively bound to the aluminum support. In an alternate procedure the binder layers are peeled off to provide a binder layer containing an image on front and back in addition to the imaged aluminum support.

EXAMPLE 11 An aluminum sheet which has a thickness of 0.006 inch is etched with a sodium hydroxide solution, washed with phosphoric acid and then anodized to produce a porous aluminum oxide coating on the aluminum sheet. This sheet is then coated with titanium dioxide in an acrylate resin binder, soaked for 5 minutes in a 5% aqueous solution of cupric nitrate, and then dried. The dry sheet is exposed to a 6 watt black light Raymaster fluorescent bulb for 60 seconds, then immersed for 150 seconds in a copperizing solution comprising 10 ml. of 1 M aqueous ascorbic acid, 10 ml. of 1 M aqueous Cu(NO and 10 ml. of 0.75 M triethanol amine in 50:50 H O--CH OH such as described in copending U.S. Ser. No. 445,743. A black image having an optical density of 0.92 results which is adherently and conductively bonded to the aluminum sheet.

In an alternative method, the aluminum sheet coated with the Ti coating is first exposed and then contacted with a cupric ion solution. On heating to about 75 C., the cuprous ion formed by reaction of the cupric ion and activated TiO disproportionates to cupric ion and copper. The latent copper image is amplified with the above mentioned copperizing solution to produce an image of good optical density which is adherently bonded to the aluminum sheet.

EXAMPLE 12 Titanium dioxide coated anodized aluminum sheets are exposed for 3 seconds on a print box, held for 10 seconds, immersed for 10 seconds in 100 ml. of 0.0005 M AgNO which contains 2.5 ml. 1 M Na NTA (sodium nitrilotriacetate) and drained for seconds. The sheets are then immersed for 15 seconds in 0.3 M Cu EDTA (prepared with CuSO and drained for 5 seconds and then developed in Ti EDTA developer for 5 seconds and finally washed, and then recycled in the Cu EDTA and Ti EDTA developer solution. The plates obtained contain images of excellent density which are adherently and conductively bound to the support.

EXAMPLE 13 A physically smooth aluminum foil which is an alloy of aluminum and 1.5% manganese is coated with a gelatin coating, dried, then coated with a layer of finely-divided zinc oxide in a polyvinyl alcohol binder, dried and then exposed through a negative.

The thus exposed plate is then immersed in an aqueous solution of 3 N silver nitrate, then contacted with an aqueous solution of 20 grams of Metol and 80 grams of citric acid per liter of water and having a pH of about 2.2, to thereby produce a silver image. The gelatin binder layer is washed from the plate to disclose a silver image adherently and conductively bound to the aluminum plate.

The following acids, which are aluminum complexing agents, are substituted in the above example for the citric acid: tartaric, maleic, gluconic, and oxalic. Similar results are obtained as when the citric acid is used. A metallic image with improved adherence to the aluminum substrate is obtained for a given processing time when the substrate is being rapid processed.

When an unalloyed aluminum support which had a physically smooth surface was used in the above example, the image washed off the aluminum support with the rest of the gelatin coating upon washing with water. The alloyed support also showed greater photographic speed than the 'unalloyed sample when exposed and processed similarly.

EXAMPLE 14 -An unsealed porous anodized aluminum plate coated with a water soluble, water permeable polyvinyl alcohol Ti0 emulsion having a thickness of 1 micron. The emulsion is dye sensitized to visible light by dipping into a solution of 2-p-dimethylaminostyryl 4 methylthiazole metho chloride and then dried as disclosed in copending patent application U.S. Ser. No. 633,689, incorporated herein by reference. This thus prepared plate is then exposed by a visible light source through a negative in projection printing procedure. The thus imaged plate is then contacted with a physical developer comprising an acidified solution of silver nitrate and Metol. After developing, the emulsion layer is washed off leaving a silver image adherently and conductively bonded to the aluminum plate. The plate is then copperized and used as a printing plate as per the procedure of Example 1.

EXAMPLE 15 An unsealed porous anodized aluminum plate coated with 4 parts by weight of titanium dioxide to 1 part by weight of a water soluble, water permeable polyvinyl alcohol to a coating thickness of 1 micron is sensitized by dipping into a solution of Neocyanine dye and then dried according to the procedure of our co-pending U.S. patent application Ser. No. 359,956, incorporated herein by reference. The plate is then exposed imagewise at a distance of 4 inches to light from a 25 watt tungsten light bulb which is filtered to remove wavelengths less than 460 millimicrons for periods of time between 3 minutes and 15 minutes to imagewise bleach the dye.

The exposed plate is then uniformly exposed to the same light source for about 5 seconds to activate the copy medium in the areas where the dye is not bleached.

The thus exposed plate is then physically developed in a solution of silver nitrate, Metol, and citric acid until the image has formed all the way through the emulsion and becomes adherently and conductively bonded to the aluminum support. The emulsion layer is then washed off to give a silver image which is a positive of the original and is adherently and conductively bonded to the support. This imaged plate is then made into a printing plate by procedures outlined in Example 1.

EXAMPLE 16 A brush grained aluminum plate is dipped in a hot chromic acid solution, washed to remove the acid, dryed and coated with 4 parts by weight of titanium dioxide to 1 part by weight of water soluble, water permeable polyvinyl alcohol to a coating thickness of about 1 micron. The coated plate is then exposed with a carbon are for one minute at a distance of 25 inches from the vacuum frame. The sheet is then immersed in the developer solution described in Example 3 wherein parts I and H are mixed just prior to use. The immersion time in the developer is 60 seconds. The developed sheet is then immediately washed with cold water to remove the photosensitive emulsion.

A series of 6 additional aluminum plates were prepared and imaged according to the above procedure except that an aluminum oxide layer was applied to the aluminum surface immediately prior to applying the photosensitive emulsion by placing the aluminum plate which has had the oxide layer removed and which has been washed in a three percent ammonium tartrate solution and a constant current passed through the plate at diiferent voltages. By increasing the voltage applied, the barrier oxide layer is increased. These tests indicated that a barrier oxide layer of 10 A. or greater is necessary in order to obtain an imaged plate without excessive fogging. These results are tabulated as follows:

When the imaged plates described above are prepared as printing surfaces by contacting with the dispersion described in Example 2, then contacted with a lacquer which adheres to the oleophilic image areas and then gummed and put on a printing press the copies produced from the printing plates having the background fog also show similar background fog.

EXAMPLES 17-22 Printing plates are prepared according to the following procedure. \An aluminum plate of untreated stock is contacted with a solution of chromic acid for about one minute to remove any aluminum oxide which might have formed on the surface of the aluminum. The plate is then rinsed in distilled water, immersed in an ammonium tartrate solution having a pH of 5.5, and anodized at the appropriate amperage and voltage to obtain a pre-determined barrier oxide thickness. The thus prepared aluminum plate is then coated with particulate titanium dioxide dispersed in a polyvinyl alcohol binder to a thickness sufficient to obtain a dried coating thickness of about /2 micron.

The thus prepared photosensitive plate is exposed to an image pattern from a light source (quartz iodide lamp) for 5 seconds duration, to be given an exposure of 80,000 meter candle seconds, producing a latent image on the plate.

The thus exposed plate is then immersed in an aqueous solution of 3 N silver nitrate for seconds, allowed to drain, then immersed in an aqueous developing solution having a pH of about 2.5 comprising the following:

Polyethylene glycol tertdodecyl thioether (surfactant) 1.0 Citric Acid 12.5

Water to a liter.

. and then immersed in a sodium thiosulfate fixing bath.

The coating is washed from the surface of the plate, a visible image of good density is produced on the thus treated medium. The silver image deposited on the surface of the aluminum plate forms a coherent silver image which is adherently bonded to the plate. Attempts to erase the visible image by means of vigorous abrasion from a pencil eraser, or by application of Scotch Brand transparent tape on the image areas and then ripping the tape oif vigorously does not remove the image from the plate. This indicates that the image is truly imbedded in the surface of the grained aluminum sheet.

The plate was then lacquered with a lithographic lacquer and put on an offset lithographic printing press and copies were run 011?.

The results are as follows:

Barrier oxide Applied Example thickness voltage number (A.) (volts) Image and print quality 17 0 0 No image and extremely high amount offog.

18 7 0.5 Very weak image and extremely high amount of fog which lacquered very poorly.

19 11 0.8 Weak image, high amount of background fogging and unsatisfactory prints.

20 14 1. 0 No fog-lacquered well to produce a good printing image, and relatively good quality prints.

21 30 2.2 No tog-lacquered very well to produce an excellent printing image, and very high quality prints.

These examples indicate that a barrier oxide layer of at least about 14 A. is necessary to produce a good printing plate. The plates of Examples 14-16 are used in an ofi'set lithographic press to produce thousands of copies from each plate.

What is claimed is:

1. A process of producing a metallic base photographic printing plate having images adherently bonded to the plate consisting essentially of 1) exposing a copy medium comprising a thin photoconductor layer deposited on a superficially roughened metallic support comprising a solvent impermeable insulating layer on the roughened surface to form an image of nuclei catalytic to deposition of metal from a physical developer in said layer, (2) physically developing by contacting the copy medium with image-forming material comprising a solution of metal ions and a chemical reducing agent for said metal ions to amplify said image to form a metallic image adherently and intimately bonded to the plate and wherein the plate thus produced is capable of being used as a printing plate on a conventional offset lithographic printing press for producing at least 5,000 prints, and (3) contacting the metal image of the thus imaged plate with a bath to increase the oleophilicity of this metal image.

2. A process as in claim 1 wherein the metallic support is composed of aluminum and a solvent impermeable layer composed of aluminum oxide formed by anodiza tion and wherein subsequent to step (2) the photoconductor layer is removed from the plate in the non-imaged areas and wherein the plate thus produced is capable of printing at least 100,000 prints on a conventional offset lithographic printing press.

3. A process as in claim 2 wherein the photoconductor is titanium dioxide or zinc oxide.

4. A process as in claim 1 wherein the contacting with image-forming materials comprises contacting with a stabilized physical developer comprising silver ions and a photographic reducing agent for the silver ions to thereby form a silver image.

5. Process as in claim 1 wherein the metal ions comprise silver ions or copper ions.

6. Process as in claim 1 wherein the surface of the support has been physically roughened.

7. Process of producing a printing plate comprising:

(1) forming a physically developable image in the photosensitive layer of a copy medium comprising said photosensitive layer comprising a photoconductor on a roughened metallic support comprising an insulating layer between the photosensitive layer and the metal of the support, the thickness of the photo sensitive layer being less than about 2 microns;

(2) physically developing by contacting said medium with image forming materials comprising a source of metal ions for a period of time sufficient to produce a coherent, metal image adherently bonded to the medium and capable of being used on a conventional ofiFset lithographic press under ordinary operating conditions to produce inked paper prints; and

(3) contacting the thus imaged plate with a bath to increase the oleophilicity of the metal image.

8. Process as in claim 7 wherein the step of increasing the oleophilicity of the metal image comprises contacting with a bath selected from the group consisting of a copperizing bath, a mercaptan compound-containing bath, an oleophilic lacquer solution and a bath containing a mercaptan compound and phosphoric acid.

9 Process as in claim 7 wherein the physically develop able image is produced in the exposed portions of the photosensitive layer.

10. Process as in claim 7 wherein subsequent to step -(2) and prior to step 3), the step of removing the photosensitive material in the non-imaged areas of the support.

11. Process as in claim 7 wherein the photoconductor comprises titanium dioxide or zinc oxide.

12. Process as in claim 7 wherein the image forming materials additionally comprise a chemical reducing agent for said metal ions.

13. Process as in claim 12 wherein the metal ions comprise silver ions.

14. Process as in claim 7 wherein the surface of the support has been physically roughened and wherein the insulating layer between the photosensitive layer and the metal of the support comprises an oxide of the metal of the support.

15. Process as in claim 14 wherein the metal of the support is aluminum and wherein the insulating layer is a solvent impermeable aluminum oxide layer having a thickness of between about 100 and 200 A. and wherein the imaged support produced in step (2) is capable of being used on a conventional offset lithographic press under ordinary operating conditions to produce at least 100,000 inked paper prints.

-16. Process as in claim 15 wherein the image forming materials comprise a stabilized physical developer comprising silver ions and a chemical reducing agent.

17. Process as in claim 7 wherein the imaged support produced in step (4) is capable of being used on a conventional offset lithographic press under ordinary operating conditions to produce at least 1000,000 inked paper prints and wherein the physical roughening is produced by brush graining.

References Cited UNITED STATES PATENTS Sanders 96-1.5 Berman 96-27 Chamberlain 96-1.5 X Shephard et al. 96-64 Mason 96-86 Freedman et al. 96-86 Jenny et al. 96-86 Butterfield 96-1 E Tomanek et al 96-86 X Tomanek 96-1.5 England et al. 96-33 Sieg et a1 96-33 Flechner 96-33 Geris 96-33 Woodward et a1 96-33 Blake 96-33 Berman 96-35 Wyman 96-48 PD NORMAN G. TORCHIN, Primary Examiner E. C. KIMLIN, Assistant Examiner US. Cl. XJR.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. I 3,809,562 Dated y 1974 InventorKs) Robert Fa Gracia et a].

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

The term of this patent subsequent to November 27, 1990,

has beenedisclaimede Signed and Scaled this TTventy-fourth Of August 1976 [SEAL] Arrest:

RU'I'H C; MASON C. MARSHALL DANN Arresting Officr Commissioner of Patents and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N 3 ,809 ,562 Dated May 7 I974 Inven R. F. Gracia L R. A. Lauqhrev and Pam] F. Tu ohey It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

CoIumn 4, Iine I2, deIete "onces" and insert in its pIace ones Column 9, Iine 23, deIete "suIfite" and insert in its pIace suIfate CoIumn 9, Iine 25, deIete "s urfact-" and insert in its pIace (surfact- CoIumn IO, Iine 2I deIete iwth" and insert in its pIace wi th CoIumn IO, Iine 58, deIete ethyIenediame" and insert in its pIace ethyIenediamine CoIumn 10, before Iine 59 which starts out A dense copper image pIease insert the foIIowing Iine H 0 to a Iiter CoIumn IO, Iines 72 and 73, deIete "However, after appIying the aqueous TiO is used without a binder" CoIumn II Iine 5I deIete "of" CoIumn II Iine 54, deIete theh" and insert in its pIace the CoIumn II Iine 62, deIete brushgraihed and insert in its pIace brush grained CoIumn I7, Iine 26, deIete 'I00O,000" and insert in its pIace IO0,000

Signed and Scaled this twenty-third 1y 0 p March 1 9 76 [SEAL] A ties t.

RUTH C. MASON C. MARSHALL DANN Arresting Officer (ommixsimzer nj'PaIents and Trademarks 

